This invention relates to a test apparatus for cigarette packing machines of the type having a plurality of spring biased, axially displaceable tappets adapted to engage the ends of a group of cigarettes and to detect, in response to the lack of a suitable displacement of one or more of said tappets, the presence of a missing or faulty (loosely packed) cigarette in said group.
The closest known prior art is exemplified by U.S. Pat. No. 3,874,227, as shown in FIGS. 1 and 2 of the drawings. The test apparatus 12 illustrated therein comprises a hollow housing 16 provided with a plurality of apertures for accommodating an equal plurality of tappets 13, 14 and 15 biased outwardly by springs 20. Each tappet has a contact head 19 adapted to be brought into engagement with a cigarette 11 in a group of cigarettes 10, and is provided at its distal end with a control head 22 accommodated, in a neutral or rest position, within a circular recess 25. A plurality of linear control ducts 27, 28 and 29 connect each row of recesses 25, and are provided with light transmitters 32, such as photo-luminescent diodes, at their one ends and with light receivers 33, such as photo transistors, at their other ends. The ducts 27, 28 and 29 are eccentrically disposed relative to the longitudinal axes of the tappets 13, 14 and 15 so that the light control beams from the transmitters 32 are able to pass through to the receivers 33 when all of the control heads 22 in a given row are displaced. In operation, the housing 16 and projecting tappets are swung into contact with a "packed" group 10 of cigarettes 11, and if one or more the tappets fails to be axially displaced, as when a missing or loosely packed cigarette is encountered, one of the control ducts will remain blocked and its associated receiver 32 will not generate a group "acceptance" signal, whereby the tested group of cigarettes is rejected.
With the arrangement of the FIGS. 1 and 2, however, only one position of the tappets 13, 14 and 15 can be tested by means of the light rays passing through the control ducts 27, 28 and 29. The practical operation of a cigarette packaging machine gives rise to considerably quantities of dust, paper fibers, tobacco residues, etc., and experience has shown that these particles tend to lodge firmly in the corners, gaps, and the like of the apparatus. As a result, when the tappets are actuated by engagement with cigarettes and axially displaced against the pressure of springs 20, they may jam and fail to return to their initial positions (shown at 14 in FIG. 1). As is obvious, such return failure gives rise to faulty test results.